dev-python/pypy3-5.8.0 as SLOT=0/58, while dev-python/pypy3-bin-5.8.0 has SLOT=0/57 and virtual/pypy3-5.8.0 depends on ...:0/57, which prevents the non-bin package from being a useful replacement of the bin package.
Sorry about the mistake. commit 12d8dec23b540a4d87935545ceb6592e2862cc1f Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Sat Jun 10 09:46:44 2017 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sat Jun 10 09:48:12 2017 virtual/pypy3: Fix subslot, #621364 commit a7561eef71cf2cfc69a8c9d55992e5456a066cf3 Author: Michał Górny <mgorny@gentoo.org> AuthorDate: Sat Jun 10 09:47:08 2017 Commit: Michał Górny <mgorny@gentoo.org> CommitDate: Sat Jun 10 09:48:11 2017 dev-python/pypy3-bin: Fix subslot, #621364